Various types of light hoisting mechanisms are known for securement to lightweight vehicles such as panel trucks, tractors, and even all terrain vehicles for lifting small loads below 1000 lbs.
Reference is made to U.S. Pat. No. 5,445,487 to illustrate a typical example of the construction of such lightweight hoists. There are several disadvantages with these hoist structures. A main disadvantage is that the lifting cable, which is positioned about the pulley secured at the top end of the boom, often will jump the pulley during operation if the load is disposed sideways of the pulley exerting a lateral pulling force on the cable. This often leads to damage and considerable downtime for repair. It also presents a danger to the operator. Another disadvantage of these hoists is that they are often incapable of pulling loads which are disposed at a distance from the hoist and often at an angle to the hoist. Although some of these hoists are provided with boom angle adjustments, these adjustments are mechanical and require a resetting each time the boom has to be disposed at a different angle.
A still further disadvantage of known lightweight booms is that often these booms are freely rotatable on their support axis and when dragging or lifting a load the boom may suddenly rotate on its support swinging the load and causing injury to personnel or to equipment in the vicinity of the boom. The load being lifted or retrieved by the hoist also often will cause the boom support to bend or break due to excessive loading and this is also hazardous.
A still further disadvantage of these lightweight booms is that they cannot be disassembled quickly to form a small transport package for ease of transportation. They are also time consuming to install on a vehicle or on a support frame and often require special brackets.